With respect to the pertinent state of the art, we refer to the book “Windkraftanlagen” [Wind power systems] by Erich Hau, 1996. This book contains a few examples of wind power systems, rotor blades for such wind power systems as well as cross sections through rotor blades according to the state of the art. The geometric profile parameters of aerodynamic profiles according to NACA are illustrated in FIG. 5.34 on page 102. According to this illustration, the rotor blade is described by a profile depth that corresponds to the length of the chord, a maximum camber (or camber ratio) that defines the maximum height of the skeleton line above the chord, a position of maximum camber, i.e., the location of the maximum camber within the cross section of the rotor blade relative to the profile depth, the maximum profile thickness that defines the maximum diameter of an inscribed circle, the center of which lies on the skeleton line, and the position of maximum thickness, i.e., the location at which the cross section of the rotor blade assumes its maximum profile thickness relative to the profile depth. In addition, the leading edge radius as well as the profile coordinates of the lower and upper side are used for describing the cross section of the rotor blade. The nomenclature from the book by Erich Hau, inter alia, is also used for the description of the cross section of a rotor blade according to the present invention.
Other rotor blades according to the state of the art are disclosed in DE 103 07 682, U.S. Pat. No. 5,474,425, U.S. Pat. No. 6,068,446 and DE 694 15 292.
The optimization of rotor blades can be realized in terms of several different aspects. The rotor blades should not only operate quietly, but also have a maximum dynamic performance in order to initiate the rotation of the wind power system at relatively low wind velocities and to reach nominal velocity, i.e., the velocity at which the nominal power of the wind power system is reached for the first time, at the lowest wind strength possible. If the wind velocity subsequently increases, it is now common practice to increase the adjustment of the rotor blades of pitch-regulated wind power systems into the wind such that nominal power is maintained while the surface area of the rotor blade exposed to the wind decreases in order to protect the entire wind power system and its parts from mechanical damage. In any case, the aerodynamic properties of the rotor blade profiles of the rotor blade of a wind power system are of the utmost importance.